This invention relates to processes for making double-ended tipless light sources for incandescent and metal vapor discharge lamps. The processes are particularly suited to be adapted to make light sources which comprise, in part, a reflective film completely covering the outer surfaces of the light sources.
A method of manufacturing a double-ended lamp particularly suitable for the utilization of the high pressure metal vapor discharge lamps is disclosed in Hansler and Fridrich U.S. Pat. No. 4,389,201 , assigned to the same assignee as the present invention and herein incorporated by reference. U.S. Pat. No. 4,389,201 discloses a glass lathe machine and a related method in which the double-ended lamp is flushed continuously with a dry gas so as to prevent contamination of the lamp components. Further, U.S. Pat. No. 4,389,201 discloses a method of accurately positioning the electrodes of the discharge lamp. The method of manufacturing U.S. Pat. No. 4,389,201 while serving its desired functions for the high pressure metal vapor discharge lamps does not find application to incandescent lamps.
One of the embodiments of the present invention is related to a method of manufacturing tipless double-ended light sources for tungsten-halogen incandescent lamps having the benefits of U.S. Pat. No. 4,389,201. Further, the present invention provides light sources which simplify the mounting structures of related incandescent and metal vapor discharge lamps. Still further, the present invention provides various methods of allowing an infrared or visible reflective coating to be applied, by means such as dipping, to the light source without causing any detrimental reactions between the ingredient comprising the reflective coating and the electrical leads including the seal members of the light source. The light source may be advantageous shaped, such as ellipsoidal, so that the benefits of the reflective coating cooperating with the incandescent filament may be fully realized. The composition of the reflective coating may be selected so as to allow a desired portion, for example visible or infrared, of the spectrum of the electromagnetic energy developed by the filament to be transmitted out of the lamp, and also to allow a desired portion (visible or infrared) of the spectrum to be reflected by the coating back toward the filament so as to increase the operating temperature of the filament. Infrared reflective films may be used to increase the efficacy or lumens per watt of the light source. Visible reflective films may be used to advantageously increase the heat for lamps such as heat lamps. The reflective coating providing increases in efficacy finds applications in the typical incandescent lamps, heat camps and stage and studio lamps having improved color rendition indices and color temperatures.
The present invention provides a shrink seal which avoids problems related to non-uniformity of the walls of the light source which may otherwise reduce the effectiveness of the reflective coating. Also, the shrink seal is formed without excessive heat that may otherwise damage the light source. The present invention further provides precise control of dimensions of the light source by utilizing molding techniques. The complete processing of various light sources of the present invention is accomplished without release of the tube forming the light source so that ddimensional control of the light sources is maintained throughout the processes. In certain embodiments, the present invention utilizes a continuous flush process during the manufacturing of the lamps to substantially eliminate any build-up of the contaminants that may otherwise occur during the process of the lamp. In other embodiments, a pump flush technique is utilized which also eliminates build-up of contaminants involved with the light source fabrication.